Low wattage quartz metal halide and miniature ceramic metal halide (HCl) lamps have been on the market for some time. These lamps are designed to be small concentrated sources of light for inclusion into reflectors for down-lighting and concentrated illumination (spots or floods). A key advantage offered by these lamps is the potential replacement of tungsten-halogen PAR or AR reflector lamps with more energy efficient metal halide lamps while preserving good color rendition, and uniform beam color. Examples of these types of lamps are described in U.S. Patent Publication Nos. 2003/0193280 and 2005/0184632.
However, metal halide lamps in reflector applications tend to exhibit strong color variations in the far field beam which are undesirable and essentially absent in tungsten-halogen PAR lamps. These color variations occur because of segregation in the electric arc of the radiating species, absorption of the salts on the burner interior surface and radiation escaping from the burner which does not impinge on the primary optical control surface. This color separation is somewhat mitigated by the use of dappled glass lenses over the output aperture of the reflector and swirl lines on the interior of the reflector. Still, it would be an advantage to improve the homogenization of the color of the emitted light across the beam pattern of the lamp.